Frequently such work stations will contain data files which need to be updated from time to time. Where the workstations are programmable and are constituted, for example, by a personal computer adapted to be connected to the host computer, the personal computer will contain computer programs which may require modifying from time to time to correct errors in the programs. Personal computer (PC) programs are normally supplied to users on magnetic diskettes. In reality the user does not buy the program but pays to the program owner a licence fee to use the PC program in accordance with the terms and conditions of the licence. If the user wishes to obtain a new version of the program, a new licence fee would be required.
Although computer programs are tested extensively before they are supplied to customers, it can and does happen that errors are found in them and schemes have been devised for handling the updating of defective programs, normally involving each program user needing to register his address with the program owner or the dealer through whom the program was obtained. The program owner or dealer then needs to contact each registered user to supply a new corrected PC program or to supply correction or patch information so that the user can change the old program by editing it. Apart from the expense to the program owner, this can mean inconvenience to the user and, especially where there are many personal computers on a single site, take a long time to install the new program on all of them.
Any solution to this upgrade problem should be cheap and quick.
IBM Technical Disclosure Bulletin, Vol. 18, No. 8, January 1976, page 2663, describes an online database level control arrangement in which a host computer updates a distributed database and ensures that each local subsystem is provided with the latest version of the data base stored at the host. When required, in an emergency procedure the host interrogates each subsystem to determine if it contains that part of the database needing to be updated. If it does, the host causes that part to be deleted at the subsystem, forcing that subsystem to obtain the latest level when it next requires that part of the database. Normal updating would occur after the subsystem had been powered off, for example during the night, by the host causing deletion of the down level data base during the power-up sequence, again forcing the subsystem to access the host for the upgraded data base when it requires to use that part of the data base.
Although there are certain similarities between data bases and computer programs, there are differences including the way in which computer programs are supplied to users and where there are various versions or releases of a computer program, it is very important that any upgraded information relating to a particular level or version is only supplied to a user authorised to be using that particular level or version.